Loud speaker structure and method of making the same



B. OLNEY Oct. 8, 1935.

LOUD SPEAKER STRUCTURE AND METHOD OF MAKING THE SAME 2 Sheets-Sheet 1 Filed April 13, 1931 INVENTOR V7 BENJAMIN OLNEY BY &

ATTORN Oct. 8, 1935. I aomav 2,016,453

LOUD SPEAKER STRUCTURE AND METHOD OF MAKING THE SAME Filed April-l3. 1931 v 2 Sheets-Sheet 2 INVENTOR BENJAMIN oLNEY BY A.

ATTORNEY Patented a. 8, 1935 UNITED STATES PATENT OFFI-E LOUD SPEAKER STRUCTURE AND METHOD OF MAKING THE SAME Benjamin Olney, Rochester, N. Y., assignor to The Stromberg-Carlson Telephone Manufacturing Company, Rochester, N. Y., a corporation of New York This invention relates to the method of manufacturing and the structure of a loud speaker.

In loud speakers of the moving coil type wherein there is employed an inner-polepiece or core and a surrounding outer polepiece or yoke spaced therefrom to receive a moving coil attached to a diaphragm, it is essential that this space between these polepieces be uniform at all points and further that this space should be restricted as much as possible consistent with the movement of the coil therein without engaging either of said polepieces. In the past, these results have been obtained by providing a spacing ring or other element which preserves the annular space between the polepieces in exact uniform relation or else the core constituting the inner polepiece has been made adjustable so that the desired exact annular space between the polepieces might be obtained.

The use of a spacing ring or other spacing element in addition to the cost of material, results in the additional cost of manufacturing and attaching such a ring to certain of the elements. Where the central core constituting the central polepiece is adjustable, much difiiculty has been encountered in looking the core in the exact position to which it has been adjusted. Furthermore if it is desired to repair the driving unit, and then reassemble it, this reassembly could not be effected without the use of a gage.

In accordance with the present invention, the loud speaker driving unit has been designed and a method of manufacturing it has been developed in which the need of a spacing ring or other spacing element has been obviated and this has been accomplished without making the central core element adjustable. A further feature of the invention resides in the method of holding the outer polepiece in laterally fixed, uniformly spaced, annular relation to the core and yet permitting repair and reassembly of the unit without the need for centering instruments. Other features will appear from the detailed description and the appended claim.

Referring to the drawings, Fig. 1 is a perspective view of a loud speaker of the present invention with parts thereof broken away to simplify disclosure and with the cone-shaped diaphragm displaced from its normal position; Figs. 1A and 1B represent different forms of moving coil terminals; Fig. 2 is a plan view of the loud speaker; Fig. 3 is a vertical section taken on the line 33 of Fig. 2; Fig. 4 is a perspective view of the U- shaped magnet and the yoke or polepiece (both having portions broken away) showing in detail the arrangement for holding the yoke against lateral movement with respect to the magnet; Fig. 5 is a cross-sectional View of the yoke showing how the centering pins are held in position; Fig. 6 is a perspective view of a protective collar for the 5 energizing field coil of the loud speaker; Fig. 7 is a view partially in sectionshowing how a gage may be used to center the yoke with respect 'to the core of the magnet; Fig. 8 is a similar View except that it shows the same gage used to center the conediaphragm bracket with respect to the yoke and the remainder of the driving unit assembly.

Referring to Fig. 1, lil designates a U-shaped magnet which is apertured at H to receive the reduced end I2 of a cylindrical core H as shown in Fig. 3. The reduced end of this core is riveted in position as shown at I4 to hold the core substantially in equally spaced relation from each of the uprights of the magnet. An energizing field coil l5 surrounds the core I3; which coil, as is well-known, comprises many turns of wire, each end of which terminates in fiat terminals l6 and I! arranged to be substantially flush with the outer surface of the coil. These terminals enable the conductors l8 and. IS (which may lead to a suitable power device) to be soldered directly thereto. When these conductors have been attached in this manner, an insulating strip 28 of paper or other suitable material is placed surrounding the coil with a tab 25 inserted in the slit 6 22 to hold the ends in position to form a collar. In practice, the length of the collar 20 is just about equal to the length of the inner space between the magnet and the yoke so that it is impossible to remove the collar 2!.) unless the driver unit is 3 disassembled.

On the free ends of the U-shaped magnet l0, there is fastened a yoke or polepiece 23 having an opening 24 of slightly larger diameter than that of the core I3. In assembling the yoke on the magnet, a gage 65, engaging the outer surface of the core 13 and the surface of the opening 24, (Fig. 4) serves to center the yoke 23 with respect to the core l3 thereby forming an air gap of exact annular dimensions. With the yoke in proper position, an angular shaped bracket 21 for supporting the cone-diaphragm is mounted on the driver unit with its opening 28 (Fig. 7) substantially concentric with the opening 24 in the yoke. This concentric relation is obtain-ed as shown in Fig. 8 when the edge of the shoulder 29 on the gage 65 engages the inner surface of the opening 28 in the bracket. When the yoke and bracket are thus properly centered, they are held clamped in this relation by means of bolts 30 passing 55 through apertures in the magnet, yoke and bracket, as best shown in Figs. 4, '7, and 8. After the yoke and bracket are thus properly centered, hardened steel pins 25 are driven through apertures 25 into the unpierced, free ends of the magnet ill, and thereafter the gage 65 is withdrawn. These pins are then forced into the ends of the magnet until their heads are below the upper surface of the yoke. Subsequently the edges of the apertures 25 are peened to hold the pins in the desired position. These pins when thus driven into the ends of the magnet prevent any lateral movement of the yoke and yet permit the driving unit to be disassembled and then subsequently reassembled while assuring an exact centering of the yoke with respect to the coil without any additional use of a gage. Nuts 3| engage the bolts 36 to permit the respective parts just mentioned to be tightly clamped in place. On the outer ends of the bracket 2?, there are mounted two clamping rings 32 and 33, between which there is clamped a flexible mounting 34 attached to the free edge of the cone-diaphragm 35. As herein disclosed, this flexible mounting comprises sections of soft leather glued or otherwise attached to the edge of the cone-diaphragm. Although leather is mentioned as a flexible mounting, it will be understood that any other material which is flexible and which has substantial damping characteristics may be used instead. It is also understood that instead of leather, an annular ring formed as an extension of the cone-diaphragm and of the same or similar material may be used as the flexible coupling between the diaphragm and the clamping rings- The diaphragm 35 may be formed of any light, rigid material such as paper which is embossed with corrugations such as 35. It has been found that better results are obtained if the material in the space between the adjacent corrugations has a flat contour instead of being of rounded contour as is usual where corrugations are embossed into a diaphragm surface to give it rigidity. As best shown in Fig. 3, the diaphragm 35 is in the form of a truncated cone on the smaller end of which there is fastened a cylindrical coil support 31 of paste board or other similar material on which there is wound a coil of fine wire. This coil and its support are adapted to move in the annular air gap formed between core l3 and the side of the opening 24 in the yoke 23. It is essential that the coil and its support move in the mentioned air gap only in a direction parallel to the axis of the core I3 and in order to insure this movement, there is fastened to the diaphragm at its truncated end a spider 38 of rigid material which is mutilated as shown in Fig. 2 to permit portions thereof to move in a direction parallel to the axis of the core and yet insure that there will be substantially no movement of the spider at right angles to this axis. This spider is fastened by means of a screw 39 to the free end of the core [3 after the coil has been properly spaced or centered in the mentioned airgap.

By reference to Figs. 1, 1A and 1B, it will be noted that the terminals 45 of the coil on the support 31 are fastened to the support and are electrically connected to flexible leadout conductors such as 4 I, each of which is preferably formed of strands of flexible conducting tinsel. In order to fasten each terminal 45 of the coil and the connected end of the lead-out conductor 4| to the support, spaced apertures such as 40 are formed in the material of the support. Thereafter, the end of the flexible conductor 4|, en.- gaged by an annular, metal tip 46, is threaded through the pair of apertures and then soldered to a terminal 45 of the coil. A drop of adhesive such as shellac is applied to the terminal 45 and the portion of the conductor 4| threaded through openings 45 to attach the junction of these con ductors to the support. Instead of fastening the junction of these two conductors to the support by threading each conductor through a pair of openings such as 40, a metal clip 4! engaging the end of the conductor 4| and piercing the material of the support may be provided, as shown in Fig. 1B. In order to insure that the terminals of the coil 45 snugly engage the support 31, a strip of paper 48 is fastened to the support covering a portion of the terminal as best shown in Fig. 1A, In this way, the lead-out from the moving coil is in no way secured to the diaphragm proper and yet the coil may be moved back and forth indefinitely without danger of breakage in the connection. The conductors ii at their free ends are fastened to conducting clip-s 42 mounted on a strip of insulation 43 in turn fastened to bracket 2?. Other conductors 44 leading to a signal current source (not shown) are respectively fastened to the other ends of the clips 42.

While in this disclosure, the magnet is referred to as U-shaped, it will be understood that a cylindrical or pot-shaped magnet which is U- shaped in cross section may be likewise used. Also the free end of the core and the opening 24 in the yoke instead of being circular, as herein shown, may be of other contour such as a rectangle or other geometric figure provided these parts are so related that they define a narrow airgap in which a movable coil may be moved.

The present disclosure is merely illustrative of the invention and is not be construed in a limiting sense except as specifically defined in the appended claim.

What I claim is:

In an acoustical device comprising a magnet U-shaped in cross section, a core fastened to said magnet extending intermediate of and substantially parallel to the free ends of said magnet, a yoke provided with an opening of similar contour but slightly larger area than the free end of said core to form therewith an airgap, a bracket, a cone-shaped diaphragm supported at its edges bysaid bracket, the smaller end of said coneshaped diaphragm having attached thereto a driving coil, the method of assembling said device and preserving uniform spacing in said airgap for said coil which comprises pinning said yoke to the previously unpierced, free ends of said mag net to retain a uniform relation between said yoke and said coil, fastening said bracket and said yoke to said magnet with said coil centered in said airgap, and flexibly support-ing said coil for movement substantially parallel to the axis of said core and without any substantial movement in a direction away from said axis.

BENJAMIN OLNEY. 

